1. Field of the Invention
This invention relates to a solenoid valve for use in ON-OFF operation and switching of a flow of fluid such as air.
2. Related Art Statement
A known solenoid valve of the type described, includes a solenoid section provided with a solenoid coil and a fixed iron core; a valve seat opposed to the solenoid section in a valve chest; a valve port of this valve seat; a movable member with a valve body, which is positioned between the solenoid section and the valve seat in the valve chest that is moved by magnetic action; and a resilient member such as a spring for biasing this movable member from the underside of the solenoid section to the valve seat. During non-excitation of the solenoid section, the movable member is urged against the valve seat by the biasing force of the resilient member or the like to close the valve port. During excitation of the solenoid section, the movable member is separated from the valve seat by the magnetic attracting action of the solenoid section against the biasing force of the resilient member or the like and attracted to the fixed iron core, thereby opening the valve port. The movable member is reciprocated between the solenoid section and the valve seat in the valve chest, whereby the valve port is ON-OFF operated, so that the flow of the fluid can be switch controlled.
The movable member is reciprocated between the solenoid section and the valve seat in the valve chest due to the magnetic attraction of the solenoid section, for ON-OFF operation of the valve port. However, since the displacement of the movable member is not regulated in a direction perpendicular to the reciprocatory movement the outer peripheral portion of the movable member comes into contact with or slides on the inner wall surface of the valve chest. A resulting disadvantage is when the outer peripheral portion of this movable member comes into contact with or slides on the inner wall surface of the valve chest, whereby the contact portion and the sliding portion are worn, the dust or debris caused by wear moves to a fluidal circuit connected to the solenoid valve, to thereby hinder other components.
A further disadvantage is that, due to the wear of the above-described contact portion and sliding portion, smooth operation of the movable member is hindered.
In the known solenoid valve, when the solenoid section is deenergized, the movable member which has been in contact with the fixed iron core is moved to the side of the valve seat by the biasing force of a resilient member such as the spring or the like, whereby the valve body abuts against the valve seat. As the valve body is fixed to the movable member, in addition to the biasing force of the resilient member such as a spring or the like, an inertial force of the valve body and the inertial force of the movable member, which is substantially larger than the former inertial force, are directly applied to the contact portion between the valve body and the valve seat. A resulting disadvantages due to the biasing force of the resilient member such as a spring or the like, and the inertial forces of the movable member and the valve body which are directly applied to the contact portion between the valve body and the valve seat, is that the contact portion between the valve body and the valve seat is worn and damaged, to thereby impair the function of the solenoid valve.
Also, in the known solenoid valve, when the movable member is brought into abutting contact with the fixed iron core of the solenoid section due to the magnetic attracting action of the solenoid section, by percussions occurring between the metallic abutting surfaces of both members, the abutting surfaces of both members are worn, so that the solenoid valve cannot be used for a long period of time and with high frequency.
As a means for preventing the foregoing disadvantages a shock-absorbing member formed of resilient material is provided on either the abutting surface of the movable member or the abutting surface of the fixed iron core of the solenoid section. However, the provision of a shock-absorbing member makes the construction complicated. Furthermore, when the shock-absorbing member is provided on the movable member, if a coupling groove is formed in the movable member and the shock-absorbing member is to be coupled into this coupling groove, then, the thickness of the shock-absorbing member is restricted by the depth of the coupling groove, i.e., the thickness of the movable member. Due to the small thickness, only a shock-absorbing member of low resiliency can be provided. Accordingly, a satisfactory shock-absorbing effect cannot be obtained.
However, if the thickness of the movable member is increased to deepen the coupling groove, whereby a shock-absorbing member having a large thickness can be provided, then, the inertial force of the movable member during its movement is increased by as much as the thickness of the movable member is increased. Therefore the impact forces of the movable member, which is aplied to the fixed iron core and the valve seat, is increased such that a satisfactory shock-absorbing effect still cannot be obtained.
Furthermore, the valve body of the above-described solenoid valve is constructed such that the valve body is moved in association with the movement of the movable member at all times. The inertial force of the movable member is larger in value than the inertial force of the valve body and the inertial force of the valve body itself is applied to the valve body to abut the valve body against the valve seat. A resulting disadvantage is that the valve body and/or the valve seat wears and is likely to become damaged.
Further, in the above-described solenoid valve, when a plurality of valve bodies, one for ON-OFF operation of a first valve port and the other for ON-OFF operation of a second valve port, are provided in the movable member, these valve bodies are supported by shock-absorbing springs in the movable member. A disadvantage of this arrangement is that the movable member becomes large in size and complicated in construction.